/Engine/Source/Runtime/SignalProcessing/Public/DSP/Encoders/IAudioEncoder.h
Must be constructed with AudioBufferSlack. Optionally, DataBufferSlack can be called with a different value depending on how often PushAudio, EncodeIfPossible, or PopData will be called.
IAudioEncoder ( uint32 AudioBufferSlack, uint32 DataBufferSlack )